The device described in JP-A 11-52136 is an example of the conventional image reading devices. This image reading device, as shown in FIG. 9, has a structure in which a LED chip 91, an optical conduction body 92, a reflector 93, a lens array 94, and a plurality of sensor IC chips 95 are accommodated inside a case 90. The optical conduction body 92 is in the form of a bar extending in the main scanning direction (direction perpendicular to the paper surface) and has light transparency. This optical conduction body 92 is so configured that if light emitted from the LED chip 91 propagates inside thereof from the light incidence surface 92a, this light is reflected by a pair of side surfaces 92c and goes out from a light outgoing surface 92b toward the reading light L of a document D. The light outgoing surface 92b extends in the longitudinal direction of the optical conduction body 92. Therefore, the entire reading line L of the document D can be adequately illuminated with the light.
The light is reflected by the document D and falls on the lens array 94. As a result, the light is converged onto a plurality of sensor IC chips 95, and an image in the location corresponding to the reading light of the document D is formed on the sensor IC chips 95. A plurality of sensor IC chips 95 have a photoelectric conversion function and output image signals at an output level corresponding to the quantity of received light. This series of operations is employed to read the image in the location corresponding to the reading line L of the document D.
The reflector 93 plays a role of preventing the light from leaking from a pair of side surfaces 92c of the optical conduction body 92 and is divided into a first and second members 93a, 93b sandwiching the optical conduction body 92 in the lateral scanning direction. Employing such a divided structure is undesirable because the first and second members 93a, 93b and the optical conduction body 92 are easily misaligned.
Accordingly, as shown in FIG. 10, a plurality of orifices 96a, 96b were provided in the optical conduction body 92 and a plurality of protrusions 97a, 97b were provided in the first and second members 93a, 93b to mate the optical conduction body with the members.
However, the following problems are associated with such conventional technology.
Thus, because the protrusions 97a, 97b are mated with the orifices 96a, 96b from both sides of the optical conduction body 92, they easily come out from both sides of the optical conduction body 92. Therefore, when the optical conduction body 92 and reflector 93 are handled to be assembled inside the case 90, the first and second members 93a, 93b are sometimes separated from the optical conduction body 92, thereby hindering the assembling operation. Furthermore, when the reflector 93 is assembled with the optical conduction body 92, for example, when the second member 93b is assembled after the first member 93a has been assembled with the optical conduction body 92, the optical conduction body 92 and the first member 93a have to be held reliably so as to prevent them from being separated. Therefore, the operation of assembling the optical conduction body 92 and reflector 93 is also difficult.
The above-described problems can be resolved if the fitting accuracy of orifices 96a, 96b and protrusions 97a, 97b is increased and they are tightly fitted together. However, even if such means is employed, the protrusions 97a, 97b are difficult to prevent reliably from being pulled out from the orifices 96a, 96b and the first and second members 93a, 93b are sometimes separated from the optical conduction body 92. The optical conduction body 92 and reflector 93 can be also bonded together by using an adhesive, but such an approach decreases productivity by adding an operation of coating the adhesive. Furthermore, if the adhesive adheres to the optical conduction body 92, the reflection pattern of the light in the respective portion becomes different from that in other portions and optical characteristics of the optical conduction body 92 might degrade.